1. Field of the Invention
The present invention relates to the field of pipe fittings or couplings for use with flexible pipes such as polyethylene ones commonly used in lawn sprinkler systems.
2. Discussion of the Background
Most commercially available pipe fittings for lawn sprinkler systems have a series of frusto-conical members or skirts. In use, these frusto-conical members are intended to perform both sealing and gripping functions (i.e., they are intended not only to prevent water from passing or leaking between them and the pipe but also to hold the pipe on the fitting under the force of the water pressure). Commonly, the pipe is crimped to actually embed or impale the edges or bases of the frusto-conical members into the plastic pipe. The problem with such dual functioning arrangements (i.e., sealing and gripping) is that they are a compromise and nearly always require exterior hose clamps to be effective, which can nearly double the material and labor costs and increase the time of installation.
That is, to get the frusto-conical members to provide a good grip to prevent blow outs, the base edges of the frusto-conical members must be as sharp as possible but this then reduces the sealing area or contact area with the pipe. To increase the sealing or contact area, the base edges can be flattened somewhat but then they do not hold as well and it is very difficult to apply enough force to crimp or impale the edges into the pipe. In effect, the compromise is that the sharper the base edges are made, the better the grip but the worse the seal. Conversely, the flatter the edges are made, the better the seal but the worse the grip. Also, for the best grip, the base edges would ideally actually pierce or pass entirely through the pipe wall for the maximum hold. However, this is obviously not possible with the frusto-conical members as each circular base edge would end up cutting the pipe completely in two. Such sealing/gripping frusto-conical members additionally tend to unseat themselves in use. That is, a high pressure or surge tends to lift or expand the pipe outwardly and off of the frusto-conical members, breaking both the seal and the grip. This is why clamps are almost always required with these types of pipe fittings.
In this light, the present invention was developed. With it, a clampless pipe fitting is provided with both superior sealing and gripping characteristics.